Question

ABCDE is a cyclic pentagon with centre of its circumcircle at point O such that AB = BC = CD and angle ABC=120°.

Calculate: ∠ BED.

Answer 1

In cyclic quadrilateral BCDE,

∠ BED +  ∠ BCD = 180°

⇒ ∠ BED + 120°  =  180°

∴ ∠  BED =  60°